This invention relates to moisture-hardening binder compositions consisting essentially of special maleic anhydride copolymers and at least difunctional organic polyamines in aldimine- and/or ketimine-blocked form, to a process for the production of these binder compositions and to their use as binders in lacquers, coating compositions and sealing compounds.
The reaction of amines with anhydrides is one which takes place very quickly, even at room temperature, leading to carboxylic acid semiamides with cleavage of the anhydride ring. The resulting, extremely short standing times have hitherto prevented polyanhydrides and polyamines from being used together in coating systems. Even 2-component binders cannot be used safely in terms of application.
A possible solution is described in DE-OS No. 2 853 477 which describes mixtures of blocked polyamines and polyanhydrides which have good standing times, but harden into crosslinked products on addition of water. Ketimines or aldimines obtained by reaction of polyamines with ketones or aldehydes are described as suitable blocked polyamines.
The polyanhydrides mentioned are compounds containing at least two cyclic carboxylic acid anhydride groups in the molecule, more especially reaction products of polyols with cyclic dianhydrides, in which the ratio of hydroxyl to anhydride groups is 1:2, or copolymers of an unsaturated cyclic anhydride with polyunsaturated compounds or .alpha.-olefins.
The olefinically unsaturated compounds used in the preparation of the copolymers are only described in very broad terms in the general description of DE-OS No. 2 853 477 without any reference to the quantitative ratios between the individual monomers which are to be used in the preparation of the copolymers. The specific disclosure of the Examples is confined to copolymers of butadiene oil and maleic anhydride in a ratio of 1:1 and to copolymers of wood oil with maleic anhydride. However, these copolymers are attended by disadvantages because combinations thereof with bisketimines or bisaldimines ultimately lead to heavily discolored products. For the rest, coating compositions containing unsaturated oil, such as butadiene oil or wood oil, as binder component lead to coatings which have a marked tendency to turn brittle and are not weather resistant.
In addition, as can be seen from the Examples of DE-OS No. 2 853 477, dimethylformamide has to be used as solvent in the processing of the binders specifically described therein, besides which unacceptable solids contents of only around 20% are used.
The object of the present invention is to provide new binder compositions based on copolymers containing anhydride groups and aldimine- and/or ketimine-blocked polyamines which are not attended by the above-mentioned disadvantages and which are suitable for the production of high-quality, moisture-hardening systems which may be hardened in reasonable times to form clear, non-yellowing, solvent-resistant films.
According to the invention, this object is achieved by the provision of the binder compositions described in detail hereinafter. In addition to organic polyamines in aldimine- and/or ketimine-blocked form, selected maleic anhydride copolymers are present in the binder compositions according to the invention.